Resistance-body.



UNITED STATES PATENT OFFICE.

GEORG EGLY, 0F BERLIN-TBEPTOW, GERMANY, ASSIGNOB TO GEBRUEDEB SIEMENS & 00., 0F BEBLm-LICHTENBERG, GERMANY, A CORPORATION OF GERMANY.

RESISTANCE-BODY.

No Drawing.

To all whom it may concern:

Be it known that I, Gnone EeLY, a German citizen, and resident of Berhn-Treptow, Germany, have invented certain new and useful Improvements in Reslstance- Bodies, of which the'following is a specification. I

This invention relates to electrical resistance bodies which are made preferably from a material known under the name of silit, consisting essentially of silicon and carbon, and which is manufactured according to a process invented by me and more fully described in my United States Patents No. 866,444 patented September 17, 1907 and No. 1,012,531 patented December 19, 1911, both assigned to Gebr. Siemens & 00., of Charlottenburg, Germany.

This material has the property of undergoing certain changes at very high temperature and in the presence of a1r,for 1nstance by an electric arcin a manner that layers will. be formed which are due to the combustion, these layers having the properties of insulating material, thereby increasing the intermediate or contact resistance and consequently decreasing the safety of the electrical connection with the ,circuit.

My invention is primarily deslgned to obviate this defect. Bes des lts use in connection with the aforementioned silit, my

invention will be found useful with allmaterials having the aforementioned properties of becoming an insulator after combustion. In case of silit especially, if small arcs are set up at the contacting points a combustion will take place resulting in the formation of silicic acid forming a thin insulating deposit upon the surface of the resistance body:

In brief my invention consists in providing an envelop or coating of carbon at the endangered points of resistance bodies of the aforementioned kind, whereby the car'- bon if sufficiently pure, will in everycase burn up in such a manner that only gaseous products are generated and no change of the intermediate resistance takes place at the points of contact.

In the case of silit a carbon envelop or Specification of Letters Patent.

Patented May 28, 1918.

Application filed February 21, 1914. Serial No. 820,270;

coating can be very easily applied, since the sil t-mass is of a nature similar to that of the carbon-mass, so that it may be easily treated under heat in an annealing furnace.

For making a silit resistance body, according to my invention, for instance, first a carbon-mass may be filled into the form, thereupon the silit-mass serving for the resistance body proper, and thereupon a carbon mass, so that the entire body thus obtained may be formed by pressing or the like and annealed in a furnace In this manner resistance bodies in the shape of plates, bars, pencils, or bodies of lenticular shape, etc., may be obtained comprising silit as a principal part, and a carbon coating at the ends thereof forming a contact terminal. 7

Such bodies for instance are used for com-- pression resistances which as known consist of a plurality of resistance elements built up in loosely coherent strata and compressed under greater or smaller pressure, the total resistance of these elements being dlepfindent from the amount of pressure app 1e Especially in resistance bodies of this kind at the contacting places of the several elements very easily small arcs will be formed soon impairing the qualities of such resistances in case they are made from pure silit. Up to the present time it has not at all been possible to successfully employ such elements from silit for resistances made by compression. This is accomplished by means of carbon coating at the contacting places according to my present invention, and therewith the great advantages of the silit for resistance bodies in general will also be utilized for this branch of manufacture, namely manufacturing electrical resistance bodies by compression.

Having thus described my invention l claim as new and desire to secure by Letters Patent of the United States 1. In a compression resistance in combination a plurality of juxtaposed resistance elements of a non-porous electrically conductive material whose conductivity is lessened under the influence of electric arcs,

and a carbon skin on the contacting faces my signature in the presence of two subof saiId elements. b scribing witnesses.

2. n a compression resistance in com 3. nation a plurality of juxtaposed resistance GEORG EGLY' 5 elements of silit and a carbon skin on the Wltnesses:

contacting faces of said elements. HENRI HASPER,

In witness whereof I have hereunto set WOLDEMAR HAUPT. 

